Half tone negatives



W. R. B. LARSENA METHOD OF MAKING SCREENS FOR USE IN PRODUCING HALF TONE NE-GATIVES. APPLiCATlON FILED SEPT. 9. 191B.

1 ,307,824=. I Patented June 24 1919.

OFFICE. q

WERNER EonEE'r jiansorrnansnn; or COPENHAGEN, DENMARK.

METHOD OF MAKING SCREEN STOR USE IN PRODUGING-HALF-TONE NEGATIVES.

p ifi n f e r m rzrtelitea June 24; 1919.

Application IiledSeptember e, 191s sejr a no asaaez.

To all whom it may concern Denmark, residing at Copenhagen, Denmark have invented new and useful Improvements in Methods of-Making Screens.

for Use in Producing Half-Tone Negatives; and I do hereby declare the following to be a full, clear, and exact description of the same.

In the producing of halftone-negatives in the art of photo-mechanical reproduction, the so-called cross-screens or line screens consisting of two ruled glass plates which are laid together in such a manner that the lines crossing one another at right angles are generally used. a certain distance from the sensitive plate and the picture which is to be reproduced through the screen is divided up into a number of points corresponding to the squares of the screen, the sizes of said points being difl'erent and contingent on the light on the various places of the picture; Applicant has on a previous occasion ascertained that a favorable elfect can be obtained by using screens on which every other cross in the cross-screen is made transparent to light,"

this provision having the effect that the printing elements otherwise formed behind the cross of the screen will disappear as regards every other cross in the high lights, whereas the shades and the darker halftones will get the ordinary character as all of the crosses will here act almost in the same manner as if photographed through an ordinary cross-screen. The consequence of this is that the printing block can beetched very deeply in the high lights as there will be a greater distance between the printing elements in these places than in'the darker parts of the picture, which facilitates the making ready and printing, especially so on ordinary kinds of paper. All this is well known.

The production of the above named screens with every other cross latticed by a clear spot presents certain difficulties and has hitherto been posslble only by photography, Even if in this manner available screens can be produced the so-called drawn or ruled screens are much preferred in which the lines are produced. through cutting or scrap- Such a screen is placed at 111g away on straight llnes an opaque film 7 v be it known that I, lN E NER: Bonner; Boson LARsEN, a sub ect of the King of.

such drawn screen being free of the photographic film contrary to what is the case in a screen produced by photography.

The invention aims at producing a drawn screen of the above named kind through ruling and will be explained below under reference to the drawing annexed in which- Figure 1 shows part of a glass plate which lsmeant for forming one half of a screen,

Fig. 2 part of another glass plate which is meant for being cemented together with the one shown in Fig. 1, i

Fig. 3 the ready made screen,

Fig. 4- one single cross at a larger scale, and

Fig. 5 a screen with transparent spots in all of the crosses.

In producing a screen according to this invention two glass plates A and B are prepared from opaque films which are cut or scraped away in a ruling machine or otherwiseso as to produce the parallel and equal as shown, these lines a being at an angle of 45 to the lines a and b, and they are spaced as shown in the drawings. In this way a plate A is produced like that shown in Fig. 1, and a plate B like that shown in Fig. 2. The two plates are then cemented together by Canada balsam orother clear cement with their film sides together, and with the lines a and b of the two. plates crossing at right angles. The two line systerns will thus intersect at right angles, and the smaller clear lines a will intersect one another in the middle of every other cross formed by the broader opaque lines in such a manner that the screen assumes the appearance shown in Fig. 3, the clear spaces in this instance being indicated by the letter 0.

As will be seen from Fig. 4, fou small screens can be produced according to this invention in which case twice as many ololique lines a are used as in the instance cited.

Having thus fully described my invention, I claim:

Method of producing drawn screens in Which crosses of the opaque lines have a transparent area, consisting in preparing two line screens having the same line distance, ruling both of them with clear lines cutting the lines of the line screens at an angle of 45 and applying one of the said line screens on the other in such a manner that the two sets of lines on the two line screens will out each other at right angles the intersections of the said clear lines fall ing in the crosses of the opaque lines of the two line screens substantially as set forth.

In testimony whereof I have afiixed my signature in presence of two witnesses.

WERNER ROBERT BUSCII LARSEN. VV'tnesses:

Vreco BLoM, F. PETERSEN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, I c Washington, D. G. 

